Capturing

Capturing the images turned out to be surprisingly easy. First, I needed to focus. I used a bright star (Atair in the Eagle) and used LiveView with maximum zoom. I played quite a while with it to make sure that I have the smallest possible star.
Next, I needed to make sure that no dew forms on the lens. The 14-24mm lens is sticking quite far out. I used some handwarmers that I fixed with one of Beth' hairbands :-)

Then I oriented the camera such that it captures some of the lake and the sky. Took one image. I needed to make sure that the images overlap sufficiently. With the Manfretto head, this wasn't a problem at all:

I just turned the horizontal knob and checked how much overlap I have. Turns out, I needed 10 turns for ~30% overlap. So, I did this all the way round. Then I moved the camera higher - making sure that there is overlap with the first layer. Now, I needed 15 turns for 30% overlap. Finally I move the camera almost all the way up and too 4 images from the zenith. These are the resulting images:

Processing

First, I loaded all images into Lightroom and made some basic adjustments (White Balance, Exposure...) I did it on one image and applied the same modifications to all other images: First in Develop Mode: Develop Settings -> Copy Settings) and then in Library mode Develop Settings -> Paste Settings.

Before:

After:

This is how all images looked afterwards:

Next, I need to merge all the images together. First, I wanted to try out if Photoshop's Photomerge can combine these images...

Much better (I only need to adjust the horizon a little - although it's still not perfect).

Now in Photoshop, I first try to straighten the horizon and create a better arc of the milky way:

Next, I crop out the sides:

I fill in the corners with the clone/stamp tool and also erase the warped flag pole on the right:

Next, I used Topaz Denoise Photoshop plugin to reduce the amount of background noise:

Before:

After

Using the Magic Wand Tool, I select the sky:

I then created a separate sky layer (Ctrl-Shift-J) and made adjustments to both the sky and the ground layer (always using adjustment layers and converting them to Clipping Masks, so that they only affect the underlying layer):

There are still a number of things that I should improve:

the horizon is still not straight

there are some artifacts left of bad alignment (e.g. horizon in the middle)

I created some stripes in the upper right corner using the clone/stamp tool